Transcript Basin and Range

Cenozoic History
• At only 66
million years
long,
– the Cenozoic is
only 1.4% of all
geologic time
– or only 20
minutes
– on our
hypothetical
24-hour clock
for geologic
time
Cenozoic Time
Scale
• In this class we use
– the term Tertiary
Period
– rather than Paleogene
and Neogene Periods
Late Cretaceous
Rifts separate Africa and South
America and then India,
Australia, Antarctica. North
America rifts from Europe.
Old Gondwana (Africa, India,
Australia) move north toward
Eurasia, closing the Tethys
Ocean and forming the AlpineHimalayan mountains.
The Atlantic lengthens /
widens, the Sevier orogeny
continues, and the Caribbean
arc forms.
Texas 65-144 Ma: continuing
shallow limestone and shale
deposition to the southeast
(from Rockies).
http://vishnu.glg.nau.edu/rcb/globaltext.html
Paleocene / Eocene
Himalayan Orogeny. Alps
and Pyrenees form.
The modern patterns of
geography appear.
Atlantic continues to open.
Rocky Mountains grow.
Texas 65 - 35 Ma: shale and
sandstone in southeast
region prograde shoreline
(from the Rockies). Volcanic
activity in Panhandle.
http://vishnu.glg.nau.edu/rcb/globaltext.html
Cenozoic Plate Tectonics
• By Eocene time,
– the Americas had completely separated
– from Europe and Africa
– but India had not yet collided with Eurasia
Oligocene and Miocene
Orogeny continues in
the Mediterranean region and
India nears its junction with
southern Asia.
Antarctica isolated.
Southwestern North America
intercepts the East Pacific Rise
and a great extensional event,
the Basin and Range orogeny
begins.
Texas 35-5 Ma: continued
sandstone/shale deposition and
progradation of shoreline
(erosion of Rockies)
http://vishnu.glg.nau.edu/rcb/globaltext.html
Cenozoic Plate Tectonics
• During Miocene time,
– the Atlantic Ocean basin continued to widen
– and India had collided with Eurasia
• The Tethys Sea between Africa and
Eurasia
– was mostly closed by this time
http://vishnu.glg.nau.edu/rcb/globaltext.html
Age of Ocean Basins
East African Rift
• A triple junction
– joins the East African
Rift System
– to the Gulf of Aden
– and the Red Sea
– Oceanic crust began
forming
• in the Gulf of Aden
about 10 million years
ago
– Red Sea rifting began
later and oceanic crust
is now forming
Orogenic Belts
• Circum-Pacific orogenic belt and the AlpineHimalayan orogenic belt are the sites of most
recent geologic and orogenic activity
Closure of the Tethys Sea
• Remember that during Mesozoic time
– the Tethys Sea separated much of Gondwana
– from Eurasia
• Closure of this sea
– took place during the Cenozoic
– as the African and Indian plates
– collided with the huge landmass to the north
Cenozoic Plate Tectonics
• Eocene time
Cenozoic Plate Tectonics
• Miocene time
The Himalayas
• During the Early Cretaceous,
– India broke away from Gondwana
– and began moving north,
– and oceanic lithosphere was consumed
– at a subduction zone
– along the southern margin of Asia
Before India Collided with Asia
• Oceanic lithosphere
– subducted beneath southern Tibet
– as India approached Asia
northern margin of India
southern margin of Tibet
India Collided with Asia
• About 40 to 50 million years ago
• India collided with Asia,
– but because India was to light to subduct,
– it thrust under Asia
Continued Convergence
• Thrusting of Asian rocks
– onto the Indian subcontinent
– accompanied continued convergence
India Moved beneath Asia
• Since about 10 million years ago,
– India has moved beneath Asia
– along the main boundary fault
– Shallow marine sedimentary rocks
• that were deposited along India’s
northern margin
• now form the higher parts of the Himalayas
The Circum-Pacific
Orogenic Belt
Evolution of the Andes Mountains
• Prior to 200 million years ago,
– the west coast of South America
– was a passive continental margin
– where huge quantities of sediment were
deposited
Evolution of the Andes Mountains
• Orogeny began when this area
– became an active continental margin
– as South America moved to the west
– and collided with oceanic lithosphere
Evolution of the Andes Mountains
• Deformation, volcanism and plutonism
continued
The North American Cordillera
• The North American Cordillera
– is one large segment of the circum-Pacific
orogenic belt
– extending from Alaska to central Mexico
• In the United States it widens to 1200 km
– stretching east-west
– from the eastern flank of the Rocky Mountains
– to the Pacific Ocean
Cordillera
• North
American
Cordillera
– and the
major
provinces
– of the
United
States
and
Canada
Sedimentary
Basins in the West
• Locations of
Proterozoic
sedimentary Basins
– in the western United
States and Canada
• Belt Basin
• Uinta Basin
• Apache Basin
Cordilleran
Mobile Belt
Antler Orogeny
in Devonian
Cordillera Evolved
• After Laramide deformation, Cordillera
continued to evolve
– large-scale block-faulting
– extensive volcanism
– vertical uplift and deep erosion
– Basin and Range
• During about the first half of the Cenozoic Era,
a subduction zone was present
– along the entire western margin of the Cordillera,
– but now most of it is a transform plate boundary
– ???
Plate Interactions Continue
http://earth.geol.ksu.edu/sgao/re
search/data/seiswus/examp
le1.gif
The Laramide Orogeny
• Third in a series of deformational events
– in the Cordillera beginning during the Late
Jurassic
• Late Cretaceous to Eocene
• Differed from the previous orogenies in
important ways
Laramide orogeny
– took place as the Farallon plate,
– buoyed up by a mantle plume
– subducted beneath North America
– at a decreasing angle
– and igneous activity shifted inland
???
Change to Shallow
Subduction
• By Early Tertiary time,
– the westward-moving North American plate
– had overridden the part of the Farallon plate,
– above the head of the mantle plume
• The lithosphere
– immediately above this plume
– was buoyed up,
– accounting for a change
– from steep to shallow subduction
Igneous Activity Ceased
• With nearly horizontal subduction,
– igneous activity ceased
– and the continental crust
– was deformed mostly by vertical uplift
Renewed Igneous Activity
• Disruption of the oceanic plate
– by the mantle plume
– marked the onset
– of renewed igneous activity
Cordilleran Igneous Activity
• The vast batholiths in
• Idaho
• British Columbia
• Sierra Nevada of California
– were emplaced during the
Mesozoic Era
– intrusive activity continued into
Tertiary
http://www.bhc.edu/academics/science/harwoodr/GEOL
102/Study/Images/BatholithsNA.gif
Tertiary
Volcanism
– more or less
continuous in
the Cordillera
– varied in
intensity,
eruptive style,
and location
– ceased
temporarily in
the area of the
Laramide
orogen
Columbia River Basalts
– an aggregate thickness of about 2500 m
– well exposed in the walls of the deep gorges
– cut by the Columbia and Snake rivers
– Some of the individual flows were truly phenomenal
• Roza flow alone covers 40,000 km2 and has been traced
about 300 km from its source
~ 20 lava flows of the
Columbia River basalts
exposed in the canyon
of the Grand Ronde
River in Washington
Cascade Range
• Some of the highest mountains in the Cordillera
are the Cascades
– California, Oregon, Washington, British Columbia
• Thousands of volcanic vents are present
– dozen large volcanoes
– Lassen Peak in California
• world's largest lava dome
• Related to subduction of the Juan de Fuca plate
http://www.cr.nps.gov/history/online_boo
ks/resedu/resedu2a.htm
Basin and Range
Basin and Range Province
• Generalized cross section of the Basin and
Range Province
– ranges are bounded by faults
Colorado Plateau
Colorado Plateau
– Paleozoic
rocks exposed
in the Grand
Canyon,
Arizona
– Mesozoic sedimentary rocks in
the Valley of the Gods, Utah
Colorado Plateau
– Mesozoic sedimentary rocks at Colorado
National Monument, Colorado
Pacific Coast
• Before the Eocene,
– the entire Pacific
Coast was a
convergent plate
boundary
– Farallon plate was
consumed at a
subduction zone
– stretched from
Mexico to Alaska
Change from Subduction
• As the North American
Plate
– overrode the Pacific–
Farallon Ridge,
– its margin became
transform faults
• the San Andreas
• and the Queen Charlotte
– alternating with
subduction zones
Extending the San Andreas Fault
• Further overriding of
the ridge
– extended the San
Andreas Fault
– and diminished the
size of the Farallon–
Plate remnants
• Now only two small
remnants
– of the Farallon plate
exist
– the Juan de Fuca and
Cocos plates
The Continental Interior
• A vast area
called the
Interior
Lowlands
– the Great
Plains
– and the Central
Lowlands
Cenozoic History of the
Appalachian Mountains
• Deformation in the Appalachians has a long
history
– began during the Late Proterozoic
– during Late Triassic time, the entire region
experienced faulting as Pangaea fragmented
Reduced to Plains
• By the end of the Mesozoic
– erosion had reduced the mountains to a plain
across which streams flowed eastward to the
ocean
Appalachians in the Tertiary
• Streams developed across the plains
during the Tertiary
Present Appalachian Topography
• Although these mountains have a long history
– their present topographic expression resulted
mainly from Cenozoic uplift and erosion
The Southern and Eastern
Continental Margins
• The Atlantic
Coastal Plain
and the Gulf
Coastal Plain
– form a
continuous belt
– from the
Northeastern
United States
to Texas
Coastal Plain Similarities
• Both areas have
– horizontal or gently seaward-dipping strata
– deposited mostly by streams flowing across them
• Seaward of the coastal plains
– lie the continental shelf, slope and rise,
– also areas of notable Mesozoic and Cenozoic
deposition
http://www.missgeo.com/directors
%20-%20mail.htm
Gulf Coast Sedimentation Pattern
• The overall Gulf Coast sedimentation pattern
– was established during the Jurassic
– and persists today
• Sediments derived from
• Cordillera
• western Appalachians
• Interior Lowlands
– were transported toward the Gulf of Mexico
– where they were deposited in terrestrial,
transitional, and marine environments
Gulf-Coastal-Plain Deposition
• Cenozoic Deposition on the Gulf Coastal Plain
– Depositional
provinces and
surface
geology
Showing
facies
changes
Cross
and
section of Eocene seaward
Claiborne Group thickening
Reservoirs for Hydrocarbons
• Many sedimentary rocks in the Gulf Coastal
Plain
– are either source rocks
– or reservoirs for hydrocarbons
http://www.spe.org/specma/binary/images/125
7473world_oil_production.gif